Dre_co - 26-6-2011 at 18:25
Hey everyone, long time lurker, first time poster here.
I have a question that involves dealing with NOx gasses that are left over from HNO3 distilling.
I have read one post on this forum about running the remaining gasses through Urea crystals. This would prevent the "suck back" you have to deal with
when using a water + baking soda solution.
My question is, How effective will this be? i have a 500ml Erlenmeyer flask that i can full with crystals , and a glass tube that i can run down to
the bottom.
My set up is an all glass distilling set up, with a vacuum adapter. using a 1:2 ratio of H2SO4 & NaNO3
I will be working in my open garage (im in japan, so out doors is not an option), and either the beaker containing the urea, or baking soda, can be
placed out the window.
Im only interested in producing (at a time) around 300ml of 70% nitric for silver refining purposes.
Please find the attached diagram of my setup, i am trying to be as safe as possible, because, honestly, these chems freak me out. hence the 20+ types
of gloves, respirators, goggles face shields, fire extinguishers, and the list goes on 
i am more than happy to answer any questions you may have.
Thanks again guys
plante1999 - 26-6-2011 at 18:30
NaNO3....
Dre_co - 26-6-2011 at 18:49
NaNO3...sodium nitrate....instead of urea crystals?
mr.crow - 26-6-2011 at 19:18
I used an inverted funnel in a beaker of NaOH solution. Honestly I don't even think I needed it. Should work fine for indoors. The first part of the
hose was discolored but that's it.
The funnel just touches the top of the solution so if it starts to suck back the level drops and air comes in.
When you dilute the RFNA to 70% do it slowly. It gets hot!
Also use the same molar amount of H2SO4 and NaNO3. Makes it easier since it always stays liquid.
hkparker - 26-6-2011 at 19:40
I have led it under a solution with disastrous results due to suck back, mr.crow's method seems like a great way around that. Urea crystals allow air
to travel back in and do an excellent job, its your best bet. It doesn't take much as it is pretty efficient, a 500ml flash is more then enough, and
set up and clean up is easy. No idea what plante1999 is talking about with sodium nitrate.
Dre_co - 26-6-2011 at 19:57
thanks, sounds like a good idea.
i am thinking to start with 70% H2SO4, this way i can bypass handling any highly conc. acids. as i have no need for RFNA.
i believe the BP will be 120, rather than 85-90 as with conc. H2SO4. other than that things should run the same.
also about the ratios im thinking, 1:1.5 because H2SO4 isnt an OTC chemical in japan.
Dre_co - 26-6-2011 at 20:04
how would the inverted funnel be held in place? with a stand? those things arent cheap. seems to me if it was just floating there, it would continue
to suck..
thanks HK, that was i was thinking. If it is so easy and efficient, why isnt there much info on the net? most people seem to bubble through a NaOH
solution.
any color change in the crystals to show saturation? thatd be cool.
smuv - 26-6-2011 at 20:18
Vac adapter --> hose --> out window.
Never a problem.
hkparker - 26-6-2011 at 20:57
My crystals just got kinda wet looking
Dre_co - 29-6-2011 at 17:45
What about lye granules? Also I have plenty of silicon tubing, but I'm thinking it's not going to handle NOx gasses well?
cyanureeves - 29-6-2011 at 18:14
i thought silicon would stand to nitric because some here mention using silicon grease for ground joints. i might be wrong and thinking of teflon. i
think plante1999 is talking about sodium nitrate as the salt to be distilled.will the urea used to absorb the nitrous gas get nitrated? sorry
should've googled first. silicon is not recommende for nitric. its time for me to distill also and i watching your post. carry on.
[Edited on 30-6-2011 by cyanureeves]
Dre_co - 29-6-2011 at 19:33
I knew silicon wouldnt last long, I was just thinking out loud.
I mentioned at the start that I was using NaNO3 as my salt. Not sure what he ment either...
Any clarification Plante1999?
[Edited on 30-6-2011 by Dre_co]